when one of your ops opens NT
1. if your partner has at least 6 cards from a suit, he bids 2 CL. then you can bid the suit that you have your high cards. if you don't have any high cards, you have to bid D.
2. if your partner bids 2 D, that means he has 5 + 5 majors. then you bid the suit, that you think, fits his hand most.
3. if your partner bids SP, that means he has 5 SP + 5 minors of CL or D. if he bids H, that means he has 5 H + 5 minors of CL or D. then you bid the suit, that you think, fits his hand most.
4. if your partner bids 2 NT, that means he has 5 + 5 minors. then you bid the suit, that you think, fits his hand most.